Mobile phones, personal digital assistants (“PDAs”), digital cameras, MP3 players, and other electronic devices utilize light-emitting diodes (“LEDs”), organic light-emitting diodes (“OLEDs”), polymer light-emitting diodes (“PLEDs”), and other SST devices for backlighting. SST devices are also used for signage, indoor lighting, outdoor lighting, and other types of general illumination. FIG. 1A is a cross-sectional view of a conventional LED die 10 that includes a substrate 12 carrying an LED structure 14. The LED structure 14 has an active region 16, e.g., containing gallium nitride/indium gallium nitride (GaN/InGaN) multiple quantum wells (“MQWs”), positioned between N-type GaN 18 and P-type GaN 20. The LED die 10 also includes a first contact 22 on the P-type GaN 20 and a second contact 24 spaced vertically apart from the first contact 22 on the front surface of the N-type GaN 18. The second contact 18 typically includes a transparent and conductive material (e.g., indium tin oxide (“ITO”)) to allow light to escape from the LED structure 14. In other conventional LED devices, the first and second contacts 22 and 24 are spaced laterally apart from one another on the same side of the LED structure 14 and/or both contacts 22, 24 may be positioned at the back side of the LED structure 14.
LED dies (e.g., the LED die 10 shown in FIG. 1A) can be coupled together in an LED module and connected to an LED driver to form an LED light fixture or luminaire. For example, FIG. 1B is a partially schematic cross-sectional view of a conventional LED module 30 including a substrate 32 carrying a plurality of LED dies 10, a converter material 34 (e.g., phosphor) that manipulates the color of light emitted by the LED dies 10, and an encapsulant or lens 36 over the LED dies 10. The LED dies 10 are connected to a common anode and cathode, which are in turn coupled to an LED driver 38 (shown schematically) that can supply current to drive the LED module 30. Additional LED modules 30 can be electrically coupled to the LED driver 38 in an LED light fixture or luminaire.
LED drivers are typically selected based on the quantity of LED modules in the luminaire and/or the operating parameters of the individual LED modules such that the driver supplies the appropriate level of current across the LED modules. If a change is made to the number of LED modules in a luminaire, a new driver must be matched to the new configuration. Accordingly, LED manufacturers must stock numerous LED drivers with incrementally increasing voltage and current outputs to match different luminaire configurations. Modifications to the circuitry connecting the LED modules to the driver may also be made to distribute the appropriate level of current across the LED modules. For example, a change in the number of LED modules may require an engineer to determine the resistance that needs to be added to the circuit to accommodate the specific configuration of the luminaire, and then the appropriate resistor must be added in the LED circuit.
Other LED luminaires include what is known as an “intelligent driver” that can recognize changes in the quantity or type of LED modules in the luminaire and adjust current output settings accordingly. Such drivers include switch mode power supplies, dedicated analog circuits, and/or dedicated memory circuits (e.g., flash memory) that identify the LED module configuration of the luminaire and adjust the current output accordingly. However, because LED drivers are already one of, if not the most expensive component in LED luminaires, the complex features of intelligent drivers only further increases the overall manufacturing cost of LED luminaires.